If you don't need recoil reduction, get the thinest one, it will be easier to fit.
Again if no recoil reduction is needed, you could refit the hard plastic butt plate you have, and it will look original, even say "Remington" on it. Hard plastci or a new bone butt plate seem to me to file and sand easier as they do not distort as they are ground down.
Just a thought, before I remove a 1" slice from a gun, I drill two 1/4 inch holes into the butt a depth of 1 1/2 inches. then cut the 1" piec off. Now I have holes in the cut piece and in the stock that align. If I even want to put the 1' back, I put dowels into the holes and tap it into perfect allighnment. If you refit it, say for your son's longer arms the is just a slight sanding needed as the wood sawdist from the cut is missing.